Production of alkylchloroboranes



' March 29, 19,60 w. H. scHEcHTr-:R ETAL 2,930,743

PRODUCTION oF ALxYLcHLRoBoRANEs Filed vec. 21, A1955 T0 AIR HBLBWONVW ELECTRODELESS DISCHARGE APPARATUS HSLSHONVH t. mw

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WILLIAM H. SCHECHTER, nov M. ADAMS fr 427% r n f5 vUnited VStates Patent. Oiiice 2,930,743 Y "Patented 'Man' 29, 1960 2,930,743 PRoDUC'rIoN'oF ALKYLCHLoRoBoRANns lower alkane, such as methane, ethane or propane, will react with boron trichloride in the presence of an electric discharge to form alkylchloroboranes. With methane and BC13 as the starting reactants, the reactions can be illus- Williaml H. Schechter, Zelienople, and Roy M. Adams, Hated as follows' Darlington, Pin, assgnors, by mesne assignments, to 919mm Callery Chemical Company, Pittsburgh, Pa., a corpo- CH+BC17- CHiBCh+HCl ration of -Pennsylvania l p 1 discharge "Application December 21, 1955, Serial No.1554,508 10 2CH4+BC1S CH3 BC1+2HC1 4'ciainis.` (ci. :o4-165) Si arg" Y Y The type of electric discharge used may be an electrode- This invention relates to` the production of alkylchloroless discharge or a glow discharge but the former type is boranes and in Vparticular it relates to a new and useful l5 preferred for best results. method of preparing methylchloroboranes such as mono- The apparatus used to carry out the above reaction is methyldichloroborane, BCH3C12,V and monochlorodimethyl shown in the accompanying schematic diagram. The reborane, B(CH3)2C1, `by -the reaction of methane with actor was of the conventional glass type used in electrodeboron trichloride in an electric discharge. less discharge experiments.

There is very little known about methods for preparing 20 In one series of experiments, methane and boron trithe alkylchloroboranes. In British Patent 618,358, it is chloride in a volume ratioof 1:1 and'3:l were subjected stated that such compounds are formed as intermediates to an electrodeless discharge at normal and elevated temin the reaction of a boron halide with an alkyl halide at peratures for various intervals of time with the results elevated temperatures in the presence of aluminum or shown in the following table:

Current in Percent Vol. of

mllliamps. Reaction C13 in gas Voltage Temp., time stream Nature of Vin kv. C. in mins. Product Initial Final Initial Final 21 32 13. 1 27 12 25. 3 10. 1 Liq.+gas.

22 23 14. a 27 ao 51. 2 as. 7 Liqfl-gas.

21 21 13. 6 130 3o 53. 1 42. 7 Liq.+gas.

22 40 13, s 132 3o 65. 2 39. 7 Lidi-gas.

36 12o '14.8 175 15 23.3 11.0 Mainiyiiquid.

zinc, but that the principal product is an alkyl borane. It is apparent from the data obtained that methane does More recently, it has been found that alkylchloroboranes 4 react with BC13 at a temperature from 27175 C. in the can be prepared by the reaction of boron trichloride with o presence of an electrodeless discharge. Infrared spectra an alkyl borane such as trimethylborane, (CH3)3B, or of thegaseous products showed strong absorption bands triethylborane, (C2H5)3B. The latter method is indirect for boron-carbon bonds and a weaker absorption band because the trialkylborane must first be prepared before for vboron-chlorine bonds. This evidence coniirmed the reaction with boron trichloride. It would therefore be presence of methylchloroboranes but no attempt was highly desirable if a method for producing alkylchloro- 45 made to isolate the pure compounds from the complex boranes, and methylchloroboranes in particular, could be gaseous mixture. Liquid products are also formed which developed which utilized readily available starting maare believed to be polymeric condensation products of terials such as boron trichloride and the lower alkanes. boron trichloride and methane. A low boron content in It is one object of this invention to provide a new and the initial gas mixture results in an increased proportion useful method for the production of alkylchloroboranes. 50 of these liquids.

A further object is to provide a simple and economical In another series of experiments, ethane and propane method for producing methylchloroboranes by the reacrespectively were subjected to an electrodeless discharge i tion of boron trichloride with methane in an electric in the presence of BC13 using a current of 22 milliamperes dismal-ge, and a voltage of 22 kilovolts with the following results:

Percent Vol. Percent Vol.

of BCI; in of Alkane in Reaction gas stream gas stream Nature of -Alkalle Used Tempq time in' Product O. mins.

Initial Final Initial Finn A still further object is to provide a method for producing alkylchloroboranes from cheap and readily available starting materials.

The above data show that both ethane and propane react with BCla under the conditions used but the rate of reaction decreases as the molecular weight of the alkane in- Other objects will appear from time to time throughout 7o creases. The products obtained in each run were identithe following specification and appended claims.

This invention is based upon the discovery that a lied by infrared spectra as complex mixtures of ethyl and propyl chloroboranes respectively.

The alkylchloroboranes provide intermediates useful for various purposes. Thus, Auten and Kraus, J.A.C.S., 74, 3398-3401 (1952), describe the reaction of dibutylchloroborane and sodium-potassium alloy in diethyl ether to produce either tributylborane or, in the presence of excess alloy, a compound MB (C4H9)2 where M is sodium or potassium. Also, Goubeau, Fiat. Review of German Sciences, Inorganic Chemistry, Part I, p. 21S-218 reports `the preparation of alkyl boronic acids by hydrolysis of alkyl haloboranes, according to the equation:

The boronic acids are in turn useful in preparing polymeric boron amides, as shown, for example, in U.S. Patent No. 2,517,944.

Having thus described this invention fully and completely as required by the patent statutes and included what is now considered to be its best embodiment, it should be understood that other variations are possible and that within the scope of the appended claims this invention may be practiced otherwise than as specifically described.

What is desired to be claimed and secured by United States Patent is:

1. A method of producing alkylchloroboranes which comprises subjecting a mixture of boron trichloride and a lower alkane in which the volume ratio of alkane to boron trichloride is about 1:1 to 3:1 to an electrodeless electric discharge, and recovering alkylchloroborane from the reaction product.

2. A method according to claim l in which the alkane is selected from the class consisting of methane, ethane and propane.

3. A method according to claim 1 in which the reaction is carried out within the temperature range from about 25 C. to about 180 C. Y

4. A method of producing methylchloroboranes which comprises subjecting a mixture of boron trichloride and methane in which the volume ratio of methane to boron trichloride is'about 1:1 to 3:1`to an electrodeless electric discharge at about room temperature, and recovering methylchloroborane from the reaction product.

References Cited in the le of this patent- UNITED STATES PATENTS Dalin July 30, 1946 OTHER REFERENCES 

1. A METHOD OF PRODUCING ALKYLCHLOROBORANES WHICH COMPRISES SUBJECTING A MIXTURE OF BORON TRICHLORIDE AND A LOWER ALKANE IN WHICH THE VOLUME RATION OF ALKANE TO BORON TRICHLORIDE IS ABOUT 1:1 TO 3:1 TO AN ELECTRODELESS ELECTRIC DISCHARGE, AND RECOVERING ALKYLCHLOROBORANE FROM THE REACTION PRODUCT. 